Last week, we looked at open loop (call setup/signaling) and closed loop (adaptive feedback loops)
In both cases, some information on some timescale about network conditions is learned by senders.
For either case, the network could also use what it learns about sources to make decisions about treating packet flows differently - at the simplest level, this is queue management and giving more precise and useful feedback than packet loss. at the next level, it might be isolating traffic flows in different queues, and scheduling packets from those queues in some fair way, perhaps providing isolation from the impact of packets in other queues, which can then lead to some guarantees about minimum throughput and perhaps maximum latency seen by a given source/destination.
As the complexity of guarantees grows, the signaling protocols and scheduling algorithms can get more expensive - these days, most of the Internet doesn't make use of anything other than the bare bones/simplest approaches, if any:-)
one point about work-conserving - trains wait until their scheduled departure time at each hop, and need an agreed clock everywhere in the network to do so accurately. on the other hand, if you are organising an outing with a bunch of autonomous people on foot/bike/car, best to synchronise at the destination, rather than departure or intermediate points, which make the coordination nightmarishly complex:-)
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